double-stud walls and wind-load
buildzilla
| Posted in Building Code Questions on
i understand that double stud wall assemblies identify either exterior or interior walls as load bearing.
as a non-engineer that makes intuitive sense to me in terms of compressive-load, but interested whether bindings at window/door openings and gussets across exterior and interior walls can be factored in to wind-load calculations.
has anyone discussed this topic with a structural-engineer?
basically, considering a double-stud assembly with 2×4 exterior and interior walls for a two-story structure, but if it just looks like a single 2×4 wall to a structural engineer, pretty sure it won’t look strong enough for the local wind-load.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Search and download construction details
Replies
Buildzilla,
What restrictions does your local code have on 2"x4" construction?
A single 2x4 wall can be up to 10' and meet code. For a single story structure or the upper floor of a 2 story structure you can space studs as much as 24" o.c.. However the first floor of a 2 story structure would need a 16" stud spacing.
So, as long as your wall height is 10' or less I really don't see an engineering issue here.
If you want a wall height between 10' and 12' the easy answer is to go with 2x6s.
Relevant Code: IRC2021 Table R602.3(5)
The inner wall will certainly help strengthen the wall in wind load if it's tied in some way to the outer, for example if the space is dense filled with cellulose insulation. But it wouldn't be worth the bother to try to engineer that. It would be way too complicated.
Note: I've got a master's degree in structural engineering but am not licensed.
in my particular case, i have two areas of concern:
(1) a walk-out basement that has framed walls supporting two stories above
(2) a great-room that has two-story walls
for the basement walls, i'm thinking it's a compressive-load issue and normal 2x4 wouldn't be sufficient, in which case, either 2x6 should be used (or potentially, engineered 2x4 members with equivalent strength of 2x6's)
generally, i'm trying to avoid the extra-thickness along the entire perimeter to conserve interior space and allow more light, but giving up the additional 2" along the perimeter is still an option.
for the great-room, could do similar strategy as with basement wall perhaps, but question for a structural-engineer, if a double-tall wall is composed of say two stacked 2x4 9' walls with top and bottom plates, is that viewed as a failed attempt to build an 18' wall with 2x4's or is it looked at as a viable assembly of two compliant 9' 2x4 walls, or other requiring special engineering scrutiny?
buildzilla,
The IRC has tables showing how many stories each type of wall stud at each spacing can be used for.
As JGSG posted, there are also maximum heights for each size of wall stud. They have to be continuous, and can not have a hinge at mid-height.